In the case of an electronic data-processing system provided in a motor vehicle, a plurality of control units are interconnected via one or more communication networks. For instance, the communication networks may have bus-like or star-shaped configurations. The control units are used to perform specific functions, e.g., fuel-injection or steering or braking functions of the motor vehicle.
For example, if two so-called event-driven communication networks are present, it is known to connect these communication networks to each other with the aid of what is commonly referred to as a gateway. The gateway has the task of converting and, if necessary, temporarily storing transmitted data, for instance, after an “interrupt” on the first communication network, in such a way that this data may then be passed on to the second communication network and retransmitted there. This conversion and buffer storage lead to time delays in the transmission of the data from the first communication network to the second communication network.
In the case of what is referred to as a time-driven communication network, a permanently predefined time schedule is provided, which stipulates for each connected control unit, a specific time slot in which this control unit may transmit data over the communication network. Furthermore, the time schedule also predefines at least one time slot in which a synchronization message is contained, with whose aid all control units linked to the communication network may be synchronized in time to each other.
If two time-driven communication networks are present, and the intention is to couple these two communication networks to each other, then it is advantageous to likewise synchronize the two communication networks in time to each other.